A conversion device for performing power conversion is provided with an inverter circuit having semiconductor switching elements connected in a full-bridge form, for example. In the inverter circuit, a pair of upper and lower arms (each including a switching element and a reverse-parallel diode) are provided in series to each other between voltage lines. As long as normal switching operation is performed, arm short-circuit in which the pair of upper and lower switching elements are turned on at the same time does not occur. However, if arm short-circuit occurs due to erroneous operation by noise, failure, or the like, overcurrent continues to flow, so that the switching elements that are still usable are broken. Considering this, a current sensor or a shunt resistor for detecting arm short-circuit current is provided in the circuit (see, for example, Patent Literature 1, Non Patent Literature 1), and when arm short-circuit current is detected, operation is stopped, to protect the switching elements.